I'm new to Denon products so I'm not sure if this is a normal thing or not. When I power up my 3805 its makes a humming noise when cut on. It has never done this until recently. Does this sound normal, its almost like its storing power and when its powered up it releases the left over energy and/or sounds like something rattleing in the power supply. Could really use your help asap so I can return it today while they have them in stock if need be.